MIMO antenna system

ABSTRACT

A multiple input, multiple output (“MIMO”) antenna system is provided for operation on a radio frequency (“RF”) module that may be used in a wireless access device. The MIMO antenna system includes a plurality of multi-band antenna elements connected to a radio in a MIMO configuration. The multi-band antenna elements and the radio are configured to operate on a RF module. A reflector is formed on the RF module to contain the plurality of multi-band antenna elements and to concentrate signal communication in a sector, the plurality of multi-band antenna elements oriented to provide a sector coverage pattern formed by beam patterns generated by each of the multi-band antenna elements.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to communication devices and moreparticularly to antennas for Multiple-Input, Multiple-Output (MIMO)media access controllers.

2. Related Art

The use of wireless communication devices for data networking continuesto grow at a rapid pace. Data networks that use “WiFi” (“WirelessFidelity”), also known as “Wi-Fi,” are relatively easy to install,convenient to use, and supported by the IEEE 802.11 standard. WiFi datanetworks also provide performance that makes WiFi a suitable alternativeto a wired data network for many business and home users.

WiFi networks operate by employing wireless access points that provideusers, having wireless (or “client”) devices in proximity to the accesspoint, with access to varying types of data networks such as, forexample, an Ethernet network or the Internet. The wireless access pointsinclude a radio that operates according to the standards specified indifferent sections of the IEEE 802.11 specification. Generally, radiosin the access points communicate with client devices by utilizingomni-directional antennas that allow the radios to communicate withclient devices in any direction. The access points are then connected(by hardwired connections) to a data network system that completes theaccess of the client device to the data network.

The three standards that define the radio configurations are:

1. IEEE 802.11a, which operates on the 5 GHz frequency band with datarates of up to 54 Mbs;

2. IEEE 802.11b, which operates on the 2.4 GHz frequency band with datarates of up to 11 Mbs; and

3. IEEE 802.11g, which operates on the 2.4 GHz frequency band with datarates of up to 54 Mbs.

The 802.11b and 802.11g standards provide for some degree ofinteroperability. Devices that conform to 802.11b may communicate with802.11g access points. This interoperability comes at a cost as accesspoints will switch to the lower data rate of 802.11b if any 802.11bdevices are connected. Devices that conform to 802.11a may notcommunicate with either 802.11b or 802.11g access points. 1In addition,while the 802.11a standard provides for higher overall performance,802.11a access points have a more limited range compared with the rangeoffered by 802.11b or 802.11g access points.

Each standard defines ‘channels’ that wireless devices, or clients, usewhen communicating with an access point. The 802.11b and 802.11gstandards each allow for 14 channels. The 802.11a standard allows for 23channels. The 14 channels provided by 802.11b and 802.11g include only 3channels that are not overlapping. The 12 channels provided by 802.11aare non-overlapping channels.

Access points provide service to a limited number of users. Accesspoints are assigned a channel on which to communicate. Each channelallows a recommended maximum of 64 clients to communicate with theaccess point. In addition, access points must be spaced apartstrategically to reduce the chance of interference, either betweenaccess points tuned to the same channel, or to overlapping channels. Inaddition, channels are shared. Only one user may occupy the channel atany given time. As users are added to a channel, each user must waitlonger for access to the channel thereby degrading throughput.

One way to increase throughput is to employ multiple radios at an accesspoint. Another way is to use multiple input, multiple output (“MIMO”) tocommunicate with mobile devices in the area of the access point. MIMOhas the advantage of increasing the efficiency of the reception.However, MIMO entails using multiple antennas for reception andtransmission at each radio. The use of multiple antennas may createproblems with space on the access point, particularly when the accesspoint uses multiple radios. In some implementations of multiple radioaccess points, it is desirable to implement a MIMO implementation in thesame space as a previous non-MIMO implementation.

Current MIMO implementations may utilize 2-3 antennas per radio. Whenmore than one antenna is used, the mutual coupling among the antennasdue to their proximity may degrade the performance of the access pointand reduce the throughput. The problem with mutual coupling is magnifiedwhen multiple radios are used in an access point.

It would be desirable to implement MIMO in multiple radio access pointswithout significant space constraints such that it would be possible tosubstitute a non-MIMO multiple radio access point with a MIMO multipleradio access point in the same space. It would also be desirable toimplement MIMO in a multiple radio access point while maximizing theperformance of the access point in coverage and quality of service(QOS).

SUMMARY

In view of the above, a multiple input, multiple output (“MIMO”) antennasystem is provided for operation on a radio frequency (“RF”) module thatmay be used in a wireless access device. The MIMO antenna systemincludes a plurality of multi-band antenna elements connected to a radioin a MIMO configuration. The multi-band antenna elements and the radioare configured to operate on a RF module. A reflector is formed on theRF module to contain the plurality of multi-band antenna elements and toconcentrate signal communication in a sector, the plurality ofmulti-band antenna elements oriented to provide a sector coveragepattern formed by beam patterns generated by each of the multi-bandantenna elements. PCB.

Other systems, methods and features of the invention will be or willbecome apparent to one with skill in the art upon examination of thefollowing figures and detailed description. It is intended that all suchadditional systems, methods, features and advantages be included withinthis description, be within the scope of the invention, and be protectedby the accompanying claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The examples of the invention described below can be better understoodwith reference to the following figures. The components in the figuresare not necessarily to scale, emphasis instead being placed uponillustrating the principles of the invention. In the figures, likereference numerals designate corresponding parts throughout thedifferent views.

FIG. 1 is a perspective view of an example of a radio frequency (“RF”)module that uses a 2-element multi-band MIMO antenna array.

FIG. 2A is a schematic diagram illustrating a top view of an example ofan S-port Wireless Local Area Network (“WLAN”) access device implementedwith an example of the RF module in FIG. 1 that includes a 3-elementmulti-band MIMO antenna array.

FIG. 2B is a schematic diagram illustrating a top view of an example ofa 12-port WLAN access device that uses an example of the RF module shownin FIG. 2A.

FIG. 2C is a schematic diagram illustrating a top view of an example ofa 16-port WLAN access device that uses an example of the RF module shownin FIG. 2A.

FIG. 3 is a schematic diagram of an example implementation of amulti-band antenna element.

FIGS. 4A-4E are schematic diagrams illustrating the use of spatialdiversity to generate a sector coverage pattern using beam patternsgenerated by each of the antenna elements in the 3-element multi-bandMIMO antenna array.

FIG. 4E is a cross-sectional view of the beam patterns shown in FIG. 4Aat broken line E-E′ of FIG. 4A.

FIG. 5 is a block diagram of an example radio that may be used in an RFmodule that includes MIMO configured multi-band antenna arrays.

DETAILED DESCRIPTION

In the following description of the preferred embodiment, reference ismade to the accompanying drawings that form a part hereof, and whichshow, by way of illustration, a specific embodiment in which theinvention may be practiced. Other embodiments may be utilized andstructural changes may be made without departing from the scope of thepresent invention.

A wireless local area network (“WLAN’) access device that uses a MIMOantenna array is disclosed. The WLAN access device may include acircular housing having a plurality of radial sectors and a plurality ofantenna arrays, each antenna array arranged within individual radialsectors of the plurality of radial sectors.

In general, the antenna arrays used in the WLAN access device includemultisector antenna systems that radiate a plurality of radiationpatterns that “carve” up the airspace into equal sections of space orsectors to assure continuous coverage for a client device incommunication with the WLANAA. The radiation pattern overlap may alsoease management of a plurality of client devices by allowing adjacentsectors to assist each other. For example, adjacent sectors may assisteach other in managing the number of client devices served with thehighest throughput as controlled by an array controller. The WLANAAprovides increased directional transmission and reception gain thatallow the WLANAA and its respective client devices to communicate atgreater distances than standard omnidirectional antenna systems, thusproducing an extended coverage area when compared to an omni-directionalantenna system.

The WLANAA is capable of creating a coverage pattern that resembles atypical omni-directional antenna system but covers approximately fourtimes the area and twice the range. In general, each radio frequency(“RF”) sector is assigned a non-overlapping channel by an ArrayController.

Examples of implementations of a WLANAA in which multiple input,multiple output (“MIMO”) schemes may be implemented, and in whichexample implementations consistent with the present invention may alsobe implemented are described in:

-   -   PCT Patent Application No. PCT/US2006/008747, filed on Jun. 9,        2006, titled “WIRELESS LAN ANTENNA ARRAY,” and incorporated        herein by reference in its entirety, and    -   U.S. patent application Ser. No. 12/269,567 filed on Nov. 12,        2008, titled “MIMO Antenna System,” and incorporated herein by        reference in its entirety.

FIG. 1 is a perspective view of an example of a radio frequency (“RF”)module 100 that uses a 2 element multi-band MIMO antenna array. The RFmodule 100 in FIG. 1 includes a printed circuit board (“PCB”) 102, RFprocessing circuitry 104, a first antenna array element 106, a secondantenna array element 108, a reflector 110, and an edge connector 112 onthe PCB 102. The 2-element multi-band MIMO antenna array in the RFmodule 100 in FIG. 1 includes two antenna elements 106, 108.

As described below with reference to FIGS. 2A-2C, eight, twelve, orsixteen RF modules 102 may be connected radially around the controllerprinted circuit board to create a 365° coverage area around thecontroller. Each RF module 100 is configured to implement a portion ofthe 365° coverage area. Each portion is substantially pie-shaped inaccordance with the substantially pie shape of the RF modules 100. Thecoverage pattern may be configured by the reflector 110, the positionand layout of the antenna elements 106, 108, and the operation of theelectronic components implemented on the RF module 100.

The reflector 110 is configured to enhance the gain/ directivity of theantenna elements 106, 108. The reflector 110 may also be shaped toenhance isolation between adjacent RF modules 100 as well asfront-to-back isolation. For example, as shown in FIG. 1, the reflector110 may be implemented as a three-sided wall that forms two corners onopposite sides of a first side positioned perpendicular to a radial axisthat may extend from a center of a circular configuration of the WLANaccess device. The other two sides of the three-sided wall may formobtuse angles with the first wall to direct radiation in the desiredcoverage pattern. The antenna elements 106, 108 may be positioned in thecorners formed by the three-sided wall of the reflector 110. Thereflector 110 may be made of any suitable material. In oneimplementation, the reflector 110 is made of an aluminum sheet.

The PCB 102 may be any suitable printed circuit board implementation.The PCB 102 shown in FIG. 1 is substantially pie-shaped to fit in acircular configuration with other RF modules 102. The reflector 110 maybe mounted on the PCB 102 with the antenna elements 106, 108 mountedwithin the reflector 110. The antenna elements 106, 108 and thereflector 110 cooperate to radiate a sector coverage pattern outward ina radial direction when mounted in an access device.

The RF processing circuitry 104 may be designed into the PCB 102 toprovide RF signal processing functions. The RF processing circuitry 104may be configured to operate with a controller to implement any suitablewireless LAN system. The RF processing circuitry 104 may communicatewith the controller via the edge connectors 112.

FIGS. 2A-2C illustrate example WLAN access devices implemented using anexample of the RF module 100 in FIG. 1 as an 8-port WLAN access device(FIG. 2A), a 12-port WLAN access device (FIG. 2B), and a 16-port WLANaccess device (FIG. 2C). The example of the RF module 100 that is usedin the implementations illustrated in FIGS. 2A-2C uses 3-elementmulti-band MIMO antenna arrays although a 2-element arrays may be usedas well. The RF modules may all be identical to one another and connectto the controller for configuration and control during implementation.In one example, the controller is configured for each WLAN access devicebased on the number of ports (8, 12, 16).

FIG. 2A is a schematic diagram illustrating a top view of an example ofan S-port WLAN access device 200 implemented with eight RF modules 202a-h, each of which includes a 3-element antenna array 206 a-c. Each RFmodule 202 a-h also includes a reflector 208, and an edge connector 210,which connects to a mating edge connector 212 on an 8-port WLANcontroller 204. The RF modules 202 a-h in FIG. 2A are configured andarranged to provide coverage patterns in eight sectors. One radiotransceiver in each of the RF modules 202 a-h communicates via thethree-element antenna array 206 a-c connected according to a MIMOscheme. The eight sectors combine to provide a 360° coverage around theWLAN access device 200.

FIG. 2B is a schematic diagram illustrating a top view of an example ofa 12-port WLAN access device 220 implemented with 12 RF modules 222 a-1.The 12 RF modules 222 a-1 each include 3-element antenna arrays similarto the RF modules 202 a-h shown in FIG. 2A. The 12 RF modules 222 a-1are connected to a 12-port WLAN controller 224.

FIG. 2C is a schematic diagram illustrating a top view of an example ofa 16-port WLAN access device 240 implemented with 16 RF modules 242 a-p.The 16 RF modules 242 a-p each include 3-element antenna arrays similarto the RF modules 202 a-h shown in FIG. 2A. The 16 RF modules 242 a-pare connected to a 16-port WLAN controller 244.

FIG. 3 is a schematic diagram of an example implementation of amulti-band antenna element 300 that may be used as a MIMO antenna array.The antenna element 300 in FIG. 3 includes two stacked Vivaldi Notchantennas 302, 304 implemented as a multi-layer board of dielectricsubstrates. The multi-layer board may include traces and patterns ofmetal on different layers of the board. In one example implementation, athree-layer board is used in the antenna element 300 shown in FIG. 3. Inexample implementations, the Vivaldi Notch antenna is a broadbandantenna structure that can cover bandwidth of 10:1 or more.

In a middle layer of the three-layer board, a ‘V’ shaped metallic layermay be formed in the shape of each notch antenna 302, 304 shown in FIG.3. A first ‘V’ shaped metallic element, which forms a top notch antenna302 includes a top curved portion 302 a and a bottom curved portion 302b. A second ‘V’ shaped metallic element, which forms the bottom notchantenna 304 includes a top curved portion 304 a and a bottom curvedportion 302 b. The top and bottom curved portions 302 a, 304 a, and 302b, 304 b, respectively, extend from a center gap 305 and 307 that formsthe ‘V’ shaped pattern. The curved portions 302 a, 302 b, 304 a, 304 bmay be formed in dimensions suitable for receiving and transmittingsignals in the frequency bands needed according to the requirements ofthe WLAN access device. In one example, the antenna elements 302, 304are dimensioned to receive and transmit signals according to the IEEE802.11a/b/g/d/n specifications.

The notch antennas 302, 304 in FIG. 3 are configured to operate withinthe space formed by the reflector 106 to provide the desired sectorcoverage pattern. The notch antennas 302, 304 used as corner antennas inthe corners of the reflector 106 are placed at a point in the reflectorcorners that put their phase centers about a quarter wavelength (λ/4)from the corresponding corner. In order for the phase center of theantenna to coincide with that of the corner of the reflector, theantenna needs to shrink in size. As such the 2.4 Ghz band resonatesoutside of the notch zone under the curved portions 302 a, 302 b of theantennas 302. The notch antennas 302, 304 in FIG. 3 may be configured toincrease the gain of the antenna array. The notch antennas 302, 304 forman array that narrows the elevation beam while the azimuth coveragestays the same, which is similar to operation of a single notch antenna.

In order to cover the 2.4 Ghz band, the top curved portion 302 a of thetop notch antenna 302 extends to form a narrowed strip that is curvedwithin the area under the top curved portion 302 a. This first narrowedstrip functions as a top 2.4 Ghz resonating arm 310 a on the top notchantenna 302. The bottom curved portion 302 b of the top notch antenna302 extends to form a narrowed strip that is curved within the areaunder the bottom curved portion 302 b. This second narrowed stripfunctions as a bottom 2.4 Ghz resonating arm 310 b on the top notchantenna 302. The top curved portion 304 a of the bottom notch antenna304 extends to form a narrowed strip that is curved within the areaunder the top curved portion 304 a. This third narrowed strip functionsas a top 2.4 Ghz resonating arm 311 a on the bottom notch antenna 304.The bottom curved portion 304 b of the bottom notch antenna 304 extendsto form a narrowed strip that is curved within the area under the topcurved portion 304 b. This fourth narrowed strip functions as a bottom2.4 Ghz resonating arm 311 b on the bottom notch antenna 304. The fournarrow strips shown in FIG. 3 are coplanar with the top and bottomcurved portions 302 a, 304 a, and 302 b, 304 b, respectively, which maybe in a middle layer of the three-layer board. However, in otherimplementations, portions of the notch antennas 302, 304 including thenarrow strips may be etched on other layers. The narrow strips may alsobe formed in other shapes suitable for capturing signals within thedesired frequency ranges.

The top notch antenna 302 may connect to a top feedline 322 a, which isformed by a metallic trace on another layer, such as on a top layer,which extends to a main feedpoint 318 via common feedline 320 fromcommon feedpoint 324. The top notch antenna 302 may connect to the topfeedline 322 a at a top notch short stub 310, which couples to the topfeedline 322 a via a top notch antenna feedline 312. The shape anddimensions of the top notch short stub 310 and the top notch antennafeedline 312 may be selected in order to provide a proper match with thefeedline all the way to the main feedpoint 318 in the frequency range ofinterest.

The bottom notch antenna 304 may connect to a bottom feedline 322 b,which is formed by a metallic trace on another layer, such as on a toplayer, which extends to a main feedpoint 318 via common feedline 320from common feedpoint 324. The bottom notch antenna 304 may connect tothe bottom feedline 322 b at a bottom notch short stub 314, whichcouples to the bottom feedline 322 b via a bottom notch antenna feedline316. The shape and dimensions of the bottom notch short stub 314 and thebottom notch antenna feedline 316 may be selected in order to provide aproper match with the feedline all the way to the main feedpoint 318 inthe frequency range of interest.

It is noted that the implementation of the multi-band antenna element300 described above is a dual-band antenna for wireless communicationpursuant to 802.11a/n and 802.11b/g/n specifications. The multi-bandantenna element 300 may be configured for implementations based on otherspecifications. In addition, the multi-band antenna element 300 usesVivaldi notch antennas; however, any suitable multi-band antennadesigned may be used. The 2.4 Ghz resonating arms are used to optimizethe coverage of signals around 2.4 Ghz. However, other suitable shapesmay be used as well.

Two or three multi-band antenna elements 300 (in FIG. 3) may be mountedin the RF module 100 (in FIG. 1) and connected to the radio transceiver.In operation, the multiband antenna elements form coverage patterns, andusing spatial diversity provides the desired sector coverage patterns.The sector coverage patterns may be configured to ensure a desiredamount of overlap of coverage as well as a desired amount of isolationin selected areas. The sector coverage patterns may be configured by theorientation of the multi-band antenna element 300 within the RF module100 (FIG. 1), and by controlling operational factors that determine thepower, sensitivity, range and other factors. Each multi-band antennaelement forms a coverage beam, which is combined with the other coveragebeams to form the sector's coverage pattern. The overlap between beamsmay be controlled along the azimuth by the use of the notch antennas.The azimuth coverage of the individual notch antennas is a function ofthe antenna space formed by the phase center and the reflector corner.

FIGS. 4A-4D are schematic diagrams illustrating the use of spatialdiversity to generate a sector coverage pattern using beam patternsgenerated by each of the antenna elements in the 3-element multi-bandMIMO antenna array.

FIG. 4A illustrates a spatial diversity 400 obtained from thecombination of the beam patterns from each antenna element. The spatialdiversity 400 in FIG. 4A is generated by an RF module 402 having threemulti-band antenna elements 404 a-c, and a reflector 406. The threemulti-band antenna elements 404 a-c may be implemented as describedabove with reference to FIG. 3. Any suitable multi-band antenna elementmay be used instead. FIG. 4A depicts a 3-element multi-band antennaarray formed by the three multi-band antenna elements 404 a-c.

The RF module 402 generates three beams 410 a-c using the threemulti-band antenna elements 404 a-c, each antenna element 404 a-cgenerating a corresponding beam 410 a-c. FIG. 4B depicts a first beam410 a generated by the first of the three antenna elements 404 apositioned in the lower-left hand corner of the reflector 406. The firstbeam 410 a radiates along a first center axis 412 a extending from thefirst antenna element 404 a. As shown in FIG. 4C, a center beam 410 b isformed by a center one of the three antenna elements 404 b. The centerbeam 410 b radiates along a second center axis 412 b extending from thecenter antenna element 404 b. As shown in FIG. 4D, a third beam 410 c isgenerated by a third of the three antenna elements 404 c. The third beam410 c radiates along a third center axis 412 c extending from the centerantenna element 404 c. The three resulting beam 410 a-c are arrange in aspatial diversity setting where the beams cover different sections ofthe sector with a desired degree of overlap.

The beams 410 a-c generated by each antenna element 404 a-c are formedby the directivity provided by the antenna elements 404 a-c and by shapeand geometry of the reflector 406. The reflector 406 is shaped in orderto provide the isolation required for the different sectors to operateat full capacity without interfering with the other sectors. Thereflector 406 also enhances the antenna gain in the desired frequencybands. The reflector 406 has two corner reflector portions as describedabove with reference to FIG. 1. One of the 3-multi-band antenna elementsis mounted in each of the two corner reflector portions, shown as 404 aand 404 c (referring to FIG. 4A). Each of the corner antennas 404 a,c isplaced at a point in the corner that puts its phase center about aquarter wavelength (λ/4) from the corner. The third (center) antenna 404b is placed in the center of the reflector 406 and generates the centerbeam 410 b.

The corner antennas 404 a,c, which form beams 410 a,b relative to thereflector corners are positioned to generate the two beams 410 a,c suchthat they overlap and are squinted from a boresight. FIG. 4E is across-sectional view of the beam patterns shown in FIG. 4A at E-E′illustrating a view of the beam patterns from a position facing theantenna arrays into the physical boresight of the antenna array 404. Itis noted that the view in FIG. 4E assumes that the view in FIG. 4A isfrom under the RF module 400 and that the RF module 400 is installedabove the users, such as on a ceiling. The view in FIG. 4E shows thefirst beam 410 a generated by the first antenna element 404 a, thecenter beam 410 b generated by the center antenna element 404 b, and thethird beam 410 c generated by the third antenna element 404 c. The firstbeam 410 a and the third beam 410 c are shown squinted from theboresight. In an example implementation, the first and third beams 410a,c may be squinted by about +/−35°, although the squinting may be anysuitable angle range. A two-element antenna array may be used resultingin the coverage pattern defined by the two overlapping corner beams 410a,b modified by configuring and orienting the antenna elements 404 a,cto generate beams that adequately cover the sector. In the 3-elementantenna array, the center antenna is included to generate threeoverlapping beams 410 a-c providing the sector coverage pattern shown inFIGS. 4A and 4E. The three overlapping beams enable MIMO operation withlow correlation between the two or three channels coupled to the radioreceiver.

FIG. 5 is a block diagram of an example radio that may be used in an RFmodule that includes MIMO configured multi-band antenna arrays. FIG. 5depicts a MIMO channel circuit 500 that may be implemented in an RFmodule 100 (in FIG. 1). Multiple MIMO channel circuits 500 may be usedin a MIMO configured RF sector implemented with the RF module 100 (inFIG. 1). Two channel circuits 500 may be configured for a 2×2 MIMOimplementation. Three channel circuits 500 may be configured for a 3×3or a 2×3 MIMO implementation.

The MIMO channel circuit 500 in FIG. 5 includes a transceiver 502, a 5Ghz receiver/transmitter pair 504 a and 504 b, a 2 Ghzreceiver/transmitter pair 505 a and 505 b, a front-end module (“FEM”)506, band selector switch 508, a diplexer 510, a high-band line 512, alow-band line 514, and a dual-band antenna 520. The MIMO channel circuit500 shown in FIG. 5 may be configured for operation as a 2 Ghz receiverand/or transmitter, or a 5 Ghz receiver and/or transmitter according to802.11a/n or 802.11g/b/n.

The transceiver 502 may be any suitable radio transceiver configured foroperation according to 802.11a/b/g/n standards. The transceiver 502 maybe switched to operate according to one of the standards and to operateas a receiver, a transmitter, or both. Based on the switch and selectedstandard, the transceiver 502 enables either the 2 Ghz receiver and/ortransmitter lines 504 a,b or the 5 Ghz receiver and/or transmitter lines505 a,b.

The dual-band antenna 502 may include any suitable multi-band antenna,including for example, a Vivaldi notch antenna array such as themulti-band antenna array described above with reference to FIG. 3. Thedual-band antenna 502 is connected to the diplexer 510. The diplexer 510receives a signal having combined high (5 Ghz) and low (2 Ghz) signals,separates the signals and couples each to corresponding high and lowconnections 512, 514, which switch between high frequency and lowfrequency signals. In the example shown in FIG. 5, the high (5 Ghz)signal is coupled to the high connection 512, and the low signal (2 Ghz)is coupled to the low connection 514.

The high connection 512 and the low connection 514 are connected to theband selector switch 508, which may be switched to determine whichsignal to receive and/or transmit and to enhance the isolation betweenthe two frequency modes. The band selector switch 508 is configured suchthat the un-selected connection is coupled to a resistor connected toground. The resistor is provided with a high resistance to provide ahigh impedance connection for the unselected signal.

The selected signal path (i.e. high or low connection) is coupled to theFEM 506. The FEM 506 conditions the signal by using power amplifiers,low noise amplifiers, and filters for the desired signal types. In oneexample, the FEM 506 may be implemented using a SE595L Dual Band 802.11nWireless LAN Font End made by SIGe Semiconductors.

The FEM 506 is connected to the 2 Ghz receiver and/or transmitter lines504 a,b or the 5 Ghz receiver and/or transmitter lines 505 a,b toreceive 2 Ghz or 5 Ghz signals from the wireless transceiver 502 overeither the 2 Ghz or 5 Ghz transmitter lines 504 a, 505 a; or to couple 2Ghz or 5 Ghz signals to the wireless transceiver 502 over either the 2Ghz or 5 Ghz receiver lines 504 b, 505 b.

It will be understood that the foregoing description of numerousimplementations has been presented for purposes of illustration anddescription. It is not exhaustive and does not limit the claimedinventions to the precise forms disclosed. For example, the aboveexamples have been described as implemented according to IEEE 802.11aand 802.11bg. Other implementations may use other standards. Inaddition, examples of the wireless access points described above may usehousings of different shapes, not just round housing. The number ofradios in the sectors and the number of sectors defined for any givenimplementation may also be different. Modifications and variations arepossible in light of the above description or may be acquired frompracticing the invention. The claims and their equivalents define thescope of the invention.

What is claimed is:
 1. A multiple input, multiple output (“MIMO”)antenna system comprising: a plurality of multi-band antenna elementsconnected to a radio in a multiple MIMO configuration, the multi-bandantenna elements and the radio operating on a radio frequency (“RF”)module; and a reflector formed to contain the plurality of multi-bandantenna elements and to concentrate signal communication in a sector,the plurality of multi-band antenna elements oriented to provide asector coverage pattern formed by beam patterns generated by each of themulti-band antenna elements, the reflector having a shape that enhancesgain/directivity of the antenna elements and isolation between RFmodules.
 2. The MIMO antenna system of claim 1 where: the shape of thereflector is defined by a three-sided wall that forms two corners onopposite sides of a first side positioned perpendicular to a radial axisextending from an opposite end of the RF module, the three-sided wallhaving an opening opposite the first side.
 3. The MIMO antenna system ofclaim 1 where: each of the plurality of multi-band antenna elementsincludes at least one notch antenna printed on a printed circuit boardwhere the multi-band antenna element is mounted perpendicular to the RFmodule with a ‘V’ pattern formed by the notch antenna open towards thesector.
 4. A wireless local area network (“WLAN”) radio frequency (“RF”)module comprising: a printed circuit board having RF processingcircuitry; a plurality of multi-band antenna elements connected to theRF processing circuitry in a multiple input, multiple output (“MIMO”)configuration; and a reflector formed to contain the plurality ofmulti-band antenna elements and to concentrate signal communication in asector, the plurality of multi-band antenna elements oriented to providea sector coverage pattern formed by beam patterns generated by each ofthe multi-band antenna elements, the reflector having a shape thatenhances gain/directivity of the antenna elements and isolation betweenRF modules.
 5. The MIMO antenna system of claim 4 where the shape of thereflector is defined by a three-sided wall that forms two corners onopposite sides of a first side positioned perpendicular to a radial axisextending from an opposite end of the RF module, the three-sided wallhaving an opening opposite the first side.
 6. The WLAN RF module ofclaim 4 where: each of the plurality of multi-band antenna elementsincludes at least one notch antenna printed on a printed circuit boardwhere the multi-band antenna element is mounted perpendicular to the RFmodule with a ‘V’ pattern formed by the notch antenna open towards thesector.
 7. The WLAN RF module of claim 4 where the RF module isconfigurable to communicate in accordance with either the 802.11an orthe 802.11bgn standards, the RF module further comprising: a diplexerconnected to each multi-band antenna element and to a high frequencyline and a low frequency line; a front end module connected to eitherthe high frequency line or the low frequency line, the front end moduleconfigured: to connect the high frequency line and the low frequencyline to a high transmit line corresponding the high frequency line and alow transmit line corresponding to the low frequency line for radiosignals being communicated from the radio to the multi-band antennaelement, and to connect the high frequency line and the low frequencyline to a high receive line corresponding the high frequency line and alow receive line corresponding to the low frequency line for radiosignals being communicated to the radio from the multi-band antennaelement.
 8. A wireless LAN access device comprising: a plurality of RFmodules radially connected to a central controller to provide a 365°coverage pattern divided into sectors of coverage pattern provided bycorresponding RF modules, each RF module including: a printed circuitboard having RF processing circuitry; a plurality of multi-band antennaelements connected to the RF processing circuitry in a MIMOconfiguration; and a reflector formed to contain the plurality ofmulti-band antenna elements and to concentrate signal communication in asector, the plurality of multi-band antenna elements oriented to providea sector coverage pattern formed by beam patterns generated by each ofthe multi-band antenna elements, where the reflector on each RF modulecomprises a shape that enhances gain/directivity of each of plurality ofthe multi-band antenna elements and isolation between each RF module. 9.The wireless LAN access device of claim 8 where the shape of thereflector on each RF module is defined by a three-sided wall that formstwo corners on opposite sides of a first side positioned perpendicularto a radial axis extending from an opposite end of the RF module, thethree-sided wall having an opening opposite the first side.